Method and device for transmitting low speed signals in optical transport system

Abstract

A method and device for transmitting low speed signals in an Optical Transport Network (OTN), including: mapping each channel of low speed signal into an ODU signal; dividing each OPUk payload area into one or more time slots, byte interleaving each channel of OPU payload into the time slots; frame interleaving the OPU justification overhead corresponding to each channel of OPU payload in different frames of OPUk justification overhead; frame interleaving the ODU overhead corresponding to each channel of OPU payload in different frames of ODUk overhead; transforming an ODUk signal containing the OPUk payload, OPUk justification overhead and ODUk overhead into an OTUn signal and transmitting the ODUk signal in an OTN. Therefore the multiplexing and de-multiplexing method and device for implementing the transparent transmission of the low speed signal in the OTN may be implemented.

1. A method for transmitting low speed signals in an Optical Transport Network (OTN), said method being implemented by a multiplexing device, said method comprising:
 mapping each channel of low speed signal into an Optical Channel Data Unit (ODU) signal at the same grade as that of the low speed signal; 
 byte interleaving each channel of Optical Channel Payload Unit (OPU) payload of ODU signal in each time slot of Optical Channel Payload Unit k (OPUk) payload area of Optical Channel Data Unit k (ODUk) signal; 
 frame interleaving the OPU justification overhead corresponding to each channel of OPU payload of ODU signal in OPUk justification overhead of different frames of ODUk signal; 
 frame interleaving the ODU overhead corresponding to each channel of OPU payload of ODU signal in ODUk overhead of different frames of ODUk signal; 
 transforming said ODUk signal into an Optical Channel Transport Unit k (OTUk) signal and transmitting said OTUk signal in an OTN; 
 wherein the index k represents a supported bit rate and the different versions of OPUk, ODUk and OTUk. 
 
     
     
       2. The method of  claim 1 , wherein:
 said process of byte interleaving each channel of OPU payload comprises: 
 dividing said OPUk payload area of ODUk signal into one or more time slots, byte interleaving each channel of OPU payload of ODU signal in each time slot of OPUk payload area of ODUk signal, and identifying the type of OPU payload of ODU signal, the size and location of the time slot occupied by each channel of the OPU payload of ODU signal by using a payload structure identifier (PSI) corresponding to a multiframe indication; 
 said process of frame interleaving the OPU justification overhead comprises: 
 frame interleaving, according to the multiframe indication, the OPU justification overhead corresponding to each channel of OPU payload of ODU signal in OPUk justification overhead of different frames of ODUk signal; 
 said process of frame interleaving the ODU overhead comprises: 
 frame interleaving, according to the multiframe indication, the ODU overhead corresponding to each channel of OPU payload of ODU signal in ODUk overhead of different frames of ODUk signal. 
 
     
     
       3. The method of  claim 2 , wherein the low speed signal comprises N channels of low speed signals having the same rate which is 1/N times that of the OPUk payload area, N is a nature number; and
 said process of byte interleaving each channel of OPU payload of ODU signal comprises: 
 dividing each OPUk payload area into N time slots, and byte interleaving N channels of OPU payload in the N time slots of each channel of OPUk payload of ODUk signal, respectively. 
 
     
     
       4. The method of  claim 3 , wherein the value of the N is 16 if the low speed signal is a Constant Bit Rate 155 (CBR155) signal; the value of the N is 4 if the low speed signal is a Constant Bit Rate 622 (CBR622) signal. 
     
     
       5. The method of  claim 2 , wherein the low speed signal comprises at least two signals of different rates;
 the size of each time slot is the greatest common divisor of the rates of the signals of different rates. 
 
     
     
       6. The method of  claim 5 , wherein the low speed signals are N channels of CBR155s and M channels of CBR622s, said ODU signal comprises an ODU155 signal and an ODU622 signal; said ODU155 signal contains OPU155 payload, OPU155 justification overhead and ODU155 overhead; said ODU622 signal contains OPU622 payload, OPU622 justification overhead and ODU622 overhead; said OPUk is an OPU1, said ODUk signal is an ODU1 signal, and N+4XM=16; and
 said process of byte interleaving each channel of OPU payload comprises: 
 dividing each OPU1 payload area into 16 time slots evenly, byte interleaving N channels of OPU155 payload and M channels OPU622 payload in each time slot respectively, and identifying, by using the PSI corresponding to the multiframe indication, the type of the OPU payload, the size and location of time slot occupied by each channel of OPU payload, wherein one channel of OPU622 payload occupies 4 time slots, one channel of OPU155 payload occupies one time slot; and 
 said process of frame interleaving the OPU justification overhead comprises: 
 frame interleaving N channels of OPU155 justification overhead and M channels of OPU622 justification overhead in the OPU1 justification overhead according to the multiframe indication; and 
 said process of frame interleaving the ODU overheads comprises: 
 frame interleaving N channels of ODU155 overhead and M channels of ODU622 overhead in the ODU1 overhead according to the multiframe indication; 
 said process of transforming the ODUk signal comprises: 
 transforming said ODU1 signal into an OTU1 signal and transmitting said OTU1 signal in an OTN. 
 
     
     
       7. The method of  claim 2 , wherein said multiframe indication is the multiframe signal generated locally and is transferred by utilizing a multiframe alignment signal (MFAS) byte in an OTU frame or other reserved bytes. 
     
     
       8. The method of  claim 2 , wherein said process of transforming the ODUk comprises:
 adding OTUk overhead to said ODUk, wherein k=1 represents an approximate bit rate of 2.5 Gbit/s, k=2 represents an approximate bit rate of 10 Gbit/s, and k=3 represents an approximate bit rate of 40 Gbit/s. 
 
     
     
       9. The method of  claim 2 , wherein the PSI corresponding to the multiframe indication comprises a payload type indication and reserved bytes distributed in different frames; the original codes or reserved codes of the payload type indication are used for indicating the type of OPU payload, and said reserved byte in the PSI corresponding to the multiframe indication are used for indicating the size and location of the time slot occupied by each channel of OPU payload. 
     
     
       10. The method of  claim 9 , wherein said payload type indication is the PSI byte corresponding to the MFAS equal to 00000000 or any byte of 1 to 255 PSI bytes corresponding to the MFAS equal to values other than 00000000. 
     
     
       11. The method of  claim 9 , wherein said reserved bytes distributed in different frames in the PSI are at least one byte of 1 to 255 PSI bytes corresponding to the MEAS equal to values other than 00000000. 
     
     
       12. The method of  claim 2 , wherein the PSI corresponding to the multiframe indication comprises the reserved bytes distributed in different frames; the reserved byte in the PSI is used for indicating the type of the each channel of OPU payload, the size and location of the time slot occupied by the each channel of OPU payload. 
     
     
       13. The method of  claim 2 , wherein said ODU overhead comprises at least a performance monitoring overhead field. 
     
     
       14. The method of  claim 2 , wherein said low speed signal is at least one of an STM-1, an OC3, an STM-4, and an OC12 signal. 
     
     
       15. A method for transmitting low speed signals in an Optical Transport Network (OTN), said method being implemented by a de-multiplexing device, said method comprising:
 obtaining a multiframe indication upon the completion of Optical Channel Transport Unit (OTU) frame synchronization; 
 separating Optical Channel Data Unit (ODU) overhead of each channel from an Optical Channel Data Unit k (ODUk) signal according to the multiframe indication; 
 separating Optical Channel Payload Unit (OPU) justification overhead of each channel from Optical Channel Payload Unit k (OPUk) justification overhead according to the multiframe indication; 
 separating OPU payload of each channel from the time slots of OPUk payload areas according to the multiframe indication and the payload structure identifier (PSI) corresponding to the multiframe indication; and 
 making a combination of the ODU overhead, OPU justification overhead and OPU payload of each channel to recover an ODU signal, and recover an original low speed signal from the ODU signal. 
 
     
     
       16. The method of  claim 15 , wherein said multiframe indication is a multiframe alignment signal (MFAS) byte in an OUT frame or other reserved bytes. 
     
     
       17. The method of  claim 15 , wherein the PSI corresponding to the multiframe indication comprises a payload type indication and reserved bytes distributed in different frames; the original codes or reserved codes of the payload type indication are used for indicating the payload type, and the reserved bytes in the PSI corresponding to the multiframe indication are used for indicating the type of OPU payload, the size and location of the time slot occupied by each channel of OPU payload. 
     
     
       18. The method of  claim 15 , wherein the PSI corresponding to the multi frame indication comprises the reserved bytes distributed in different frames; the reserved bytes in the PSI are used for indicating the type of OPU payload, the location and size of the time slot occupied by each channel of OPU payload. 
     
     
       19. The method of  claim 15 , wherein said low speed signal is at least one of an STM-1, an OC3 signal, an STM-4 signal and an OC12 signal. 
     
     
       20. A device for transmitting low speed signals in an Optical Transport Network (OTN), comprising:
 more than one synchronization physical interface, for transforming each channel of signal into a Constant Bit Rate (CBR) parallel clock signal and CBR parallel data; 
 more than one mapping module, for receiving said CBR parallel clock signal and said CBR parallel data sent from said corresponding synchronization physical interface, mapping said parallel clock signal and data into an Optical Channel Payload Unit (OPU) frame, encapsulating the OPU with Optical Channel Data Unit (ODU) overhead, and outputting an ODU parallel clock signal and ODU parallel data; 
 a multiplexing module, for receiving said ODU parallel clock signal and ODU parallel data sent from said more than one mapping module, interleaving each channel of OPU payload in corresponding time slots of Optical Channel Payload Unit k (OPUk), frame interleaving each channel of OPU justification overhead in the justification overhead of OPUk of different frames according to a multiframe indication, and fulfilling the interleaved multiplexing of all ODU overhead according to the multiframe indication to obtain an ODUk signal and clock signal; 
 a line module, for receiving said ODUk signal and clock signal sent from the multiplexing module, transforming the ODUk signal into an Optical Channel Transport Unit k (OTUk) signal and outputting the OTUk signal; 
 a timing generator, for providing a local timing signal for said mapping modules, multiplexing module and line module. 
 
     
     
       21. A device for transmitting low speed signals in an Optical Transport Network (OTN), comprising:
 a line module, for receiving an Optical Channel Transport Unit k (OTUk) signal and transforming said OTUk signal into an Optical Channel Data Unit k (ODUk) signal; 
 a de-multiplexing module, for receiving said ODUk signal sent from said line module, separating the ODU overhead of each channel from said ODUk signal, separating the Optical Channel Payload Unit (OPU) justification overhead of each channel from the Optical Channel Payload Unit k (OPUk) justification overhead and separating the OPU payload information of each channel from the time slots of OPUks so as to obtain an ODU signal of each channel; 
 more than one de-mapping module, for respectively receiving ODU signals of all channels which are sent from the dc-multiplexing module, recovering a Constant Bit Rate (CBR) parallel clock signal and CBR parallel data; 
 more than one synchronization physical interface, for respectively receiving said CBR parallel clock signal and CBR parallel data sent from all de-mapping modules and recovering a ultimate client signal CBR; 
 a timing generator, for providing a local timing signal said de-mapping module, de-multiplexing module and line module. 
 
     
     
       22. A device for transmitting low speed signals in an Optical Transport Network (OTN), comprising;
 more than one synchronization physical interface, for transforming each channel of Constant Bit Rate (CBR) signal into a CBR clock signal and CBR parallel data; for receiving a CBR parallel clock signal and CBR parallel data and recovering a CBR signal; 
 more than one mapping/de-mapping module, for receiving the CBR clock signal and CBR parallel data sent from the corresponding synchronization physical interface, mapping the CBR parallel clock signal and CBR parallel data into an Optical Channel Payload Unit (OPU) frame, encapsulating the OPU with Optical Channel Data Unit (ODU) overhead, and outputting an ODU parallel clock signal and ODU parallel data; and for respectively receiving ODU signals of all channels, recovering a CBR parallel clock signal and CBR parallel data from an OPU payload area and obtaining, and sending the recovered CBR parallel clock signal and CBR parallel data to the synchronization physical interfaces; 
 multiplexing/dc-multiplexing module, for receiving said ODU parallel clock signal and ODU parallel data sent from the mapping/de-mapping module, interleaving each channel of OPU payload in corresponding time slots of Optical Channel Payload Unit k (OPUk), frame interleaving each channel of OPU justification overhead in the justification overhead of OPUk of different frames according to a multiframe indication, and fulfilling the interleaved multiplexing of all ODU overhead according to the multiframe indication to obtain an Optical Channel Data Unit k (ODUk) signal and clock signal; and for receiving an ODUk signal, separating the ODU overhead of each channel from the received ODUk signal, separating the OPU justification overhead of each channel from the OPUk justification overhead and separating the OPU payload information of each channel from the time slots of OPUks so as to obtain an ODU signal of each channel, and sending the obtained ODU signal to the mapping/de-mapping module; 
 a line module, for receiving said ODUk signal and clock signal sent from said multiplexing/de-multiplexing module, transforming said ODUk signal into an OTUk signal and outputting the OTUk signal; for receiving an Optical Channel Transport Unit k (OTUk) signal, transforming the received OTUk signal into an ODUk signal, and sending the ODUk signal to said multiplexing/dc-multiplexing module; 
 a timing generator, for providing a signal for said mapping/de-mapping modules, multiplexing/de-multiplexing module and line module.